Geochemical characteristics of metamorphic rocks in the HPM belt along the southern margin of Sulu terrane and their geological implications
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P588.3 P59

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    Abstract:

    The HP metamorphic belt along the southern margin of Sulu terrane is made up of a middle temperature-high pressure metamorphic slice and alow temperature-high pressure metamorphic slice. The former slice consists of gravel-bearing phengite feldspar quartzite, mica feldspar quartz schist, marble-phosphate rock and phengite albite quartz schist in upward succession, whereas the latter consists of feldspar quartz schist and albite quartz schist. In schists, the end_member component of plagioclase is albite, the feldspar phenocrysts have features of volcanic crystal fragments, and the zircon has magmatic rhythm crystallization zoning and high Th/U ratio (>0.5). In addition, the schists exhibit high SiO2 and Na2O+K2O, low CaO, enrichment of LREE with strong fractionation, depletion of HREE with weak fractionation, δEu between 0.13 and 0.47, and significant negative Nb, P and Ti anomalies. The schists are plotted in the alkaline field in a SiO2 versus A·R discrimination diagram, in the A-type field in a (K2O+Na2O)/CaO versus Zr+Nb+Ce+Y discrimination diagram. The schists in the medium temperature-high pressure metamorphic slice and in the low temperature_high pressure metamorphic slice are plotted in the peraluminous field and the metaluminous field respectively in a A/CNK versus A/NK discrimination diagram. It is thus considered that the protoliths of the three sorts of schists are acid volcanic rocks, and that the rock type and genetic type of the volcanic rocksare peraluminous to metaluminous alkaline rhyolite and A type igneous rocks, respectively. According to the major and trace element discrimination diagrams, the volcanic rocks were formed in an extensional plate environment and might have been an accessory product during the breakup of Rodinia continent and the formation of Yangtze intracontinental rift in Neoproterozoic.

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戚学祥 许志琴 齐金忠,2005,苏鲁地体南部高压变质带岩石地球化学特征及其地质意义[J].岩石矿物学杂志,24(5):476~484. QI Xue-xiang~,XU Zhi-qin~,QI Jin-zhong~,2005,Geochemical characteristics of metamorphic rocks in the HPM belt along the southern margin of Sulu terrane and their geological implications[J]. Acta Petrologica et Mineralogica,24(5):476~484.

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  • Received:July 05,2005
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